Preparation of specialty naphthas from high sulfur crudes



Sept. 4, 1956 LE ROI E. HUTCHINGS 2,761,315

PREPARATION OF SPECIALTY NAPHTHAS FROM HIGH SULFUR CRUDES Filed June 17,1953 2 Sheets-Sheet l GRUDE PETROLEUM FRAGT/OIVA T/OIV I VIRGIN IVA PHTI-IA FRACTION H Y DRODE 3 UL F UIPIZA TIO/V REGYCLE STABILIZATIONCHEM/GAL TREATMENT FRAGT/O/VAT/O/V FIG.

INVEN TOR.

BY LEROI E. I-IUTGHI/VGS ATTOR/V Y P 4, 1956 LE ROI E. HUTCHINGS2,761,815

PREPARATION OF SPECIALTY NAPHTHAS FROM HIGH SULFUR CRUDES Filed June 17,1953 2 Sheets-Sheet 2 Q0 V 0 mt m1 ot 01 f a a Q V- O E t J 91 2 1 Q a QN T i k Q .i Q 1 T W l x V 8 E RI INVENTOR.

LE ROI E. HUT OHM/65 ATTOR/V r United States Patent 'Office 2,761,815Patented Sept. 4,1956

PREPARATION OF SPECIALTY NAPHTHAS FROM HIGH SULFUR Le Roi E. Hntchings,Crystal Lake, 111., assignor to The Pure Oil Company, Chicago, 111., acorporation of Ohio Application June 17, 1953, Serial No. 362,374

4 Claims. (Cl. 1962) The present invention relates to the preparation ofrubber solvents, VM & P spirits, mineral spirits, and petroleurnnaphthas which will pass themost severe corrosion tests and are low insulfur content.

Crude petroleum is the source of a large number of products ranging fromsimple distillation products including pure hydrocarbons to highmolecular weight natural and synthetic resins, elastomers, and polymersproduced through physical and chemical transformations. Widely knownpetroleum derived products include' gasoline, kerosene, diesel fuels,lubricating oils, and heavy tars. in many instances, the productsobtained from petroleum are employed as reactants in the synthesis ofadditional petroleum derivatives and chemicals and a large number ofproducts of petroleum are used directly without extended treatment ormodification. Petroleum naphthas comprise a wide variety of such latterproducts used extensively in the dyeing, rubber, extraction, protectivecoating, and allied industries. A large portion of the petroleumnaphthas used is the straight run naphthas which are selected fractionsof the lower boiling, more volatile constituents of crude petroleum Thepresent invention is particularly directed to a'method of prepar-' ingsuch straight run naphthas and to naphtha compositions of this varietyand, accordingly, the term naphthas as used herein shall mean straightrun petroleum naphthas.

If the preparation of naphthas from petroleum is confined to physicalmeans, the products inevitably contain other types of organic andinorganic compounds'dlle to the complex nature of petroleum which havebeen found to be deleterious as far as certain end uses of the naphthasare concerned and necessitate the application of additional refiningsteps. Even with such additional refining, it is exceedingly difiicultto prepare naphthas which meet. the exacting specificationsthat havebeen established 'by the industry. Of these deleterious non-hydrocarboncom pounds the sulfur and sulfur-containing constituents are generallythe most bellicose and cling tenaciously to any environment in whichthey exist, imparting objectionable odor, corrosiveness, color, and'otherphys'ical and chemical properties thereto. The odor of naphthasisimportant; however, no standard test'exists to cover this property andthe odor of a well refined naphtha is generally de scribedassweet.

Tests have been devised to dete tively and qualitatively the prfe'sencbe e odious cornpounds in an attempt to control thejp op andciuality ofnaphthas from petroleum sources; Eorthis'purp'os'e, various copper stripcorrosion tests andthej fnp'ctgrff test have been used. Proceduresestablished by ,S, may be used to determine the content ariddistributionof these sulfur compounds. Perhaps the most critical 'and rigorousqualitative test for determining the presence 'of sulfur compounds innaphthas is the distillation-corro sion test, known also as thePhiladelphia test, the Amsco corrosion test, or the full boiling rangecorrosion teSt by any name, a species of copper strip corrosionf-t'est';'The test, Widely applied by the manufacturers,"distributors,

' ,e b th, quan i aand users of specialty naphthas, is carried out bythe addition of a small pure copper coupon to an ordinary A. S. T. M.distillation flask containing cc. of the naphtha to be tested. Thecopper strip is so positioned in theflask that one end of the stripcontacts the residue at the end of the distillation, and thedistillation is conducted according to A. 'S. T. M. D86-38 as describedin A. S. T. M. Standards on Petroleum Products and Lubricants, publishedby the American Society for Testing Materials, Philadelphia,Pennsylvania.

' At the completion of the test, wherein the flask has been heated todryness, the color of the copper strip is an indication of the relativeamount of corrosive sulfur compounds present in the naphtha sample. Anegative test is shown by the presence of a very slight or no tarnish onthe strip and stamps the naphtha as satisfactory. If the copper stripbecomes moderately tarnished or blackerred, the results are interpretedas positive or unsatisfactory. The production of a slightly tarnished orslightly colored or corroded strip, indicated by a dark orange withpeacock colorations thereon, is termed borderline and as such denotes anaphtha which is not acceptable and must be further refined. The marketis limited for off-specification naphthas and further refining isexpensive since even then there is no assurance that the product willpass thesevere distillation-corrosion test.

- The subjection of high sulfur content naphthas to various'refiningoperations which may include copper oxide slurry treating, sweeteningmethods, or extraction methods, or the recycling of rejectedoff-specification naphthas back through such a process, does not produceacceptable naphthas because the content of sulfur compounds is notreduced sufiiciently. In addition to the corrosion test, a total sulfurcontent specification must be met. High sulfur content naphthas usuallyhave a poor odor as Well as other undesirable properties. If straightrun naphthas from high 'sulfur crudes are subjected to other more severerefining methods, the resulting products do not pass thedistillation-corrosion test; Even subjecting these naphthas to the usualdesulfurization treatments involving vapor or liquid phase contact withclay or catalytic materials having strong afiinity for effectingdesulfur izat-ion does not produce a satisfactory product.

The present "invention is directed to the discovery of a method ofproducing low sulfur, sweet, non-corrosive naphthas'from high sulfurpet-roleums by applying a combination refining treatment to suchproducts. It has been found that in "order to prepare satisfactoryspecialty naphthas which meet the rigorous corrosion tests, refiningmethods must be used which not only attack such sulfur compounds ashydrogen sulfide, mercaptans, free sulfur, and disulfides, but alsoattack efficiently the so-ca-lled thermally stable sulfur compoundsincluding the higher molecular weight cyclic, heterocyclic, polymeric,and aromatic type sulfur compounds. The method of this inventioncomprises a combination treatment of the corrosive naphthas with first acatalytic hydrodesulfurization' treatment followed by a chemicaltreatment.

Accordingly, a fundamental object :of this invention is to provide acombination process for the production of naphthas which are free fromcorrosive sulfur compounds from crude petroleum containing sulfurcompounds.

A second object of this invention is to provide a method of producingnaphthas which pass the distillati ncorrosi-on test.

A third object of this invention is to produce naphtha products passingthe distillation-corrosion test from high sulfur crudesl A fourth objectis to provide a combination hydrodesulfurization and chemical treatingprocess to produce acceptable sweet, odor-free specialty naphthas.

These and other objects will become apparent as the description thereofproceeds.

In the attached drawings,

Figure l is a schematic flow diagram illustrating the genericembodiments of the invention, the relationship of the catalytic andchemical processes to each other and to the products produced therefrom.V

Figure 2 is a flow diagram illustrating the application of thecombination process to a naphtha feed. 7

In carrying out the present invention, thecrude oil, particularly ahigh'sulfur crude oil containing from 1.0 to 3.0 weight per cent ofsulfur, is fractionated to remove a virgin or straight run naphthafraction boiling from about 100 to 500 F. and preferably from about 110to 450 F. The boiling range of the naphtha fraction removed fortreatment in accordance with thisinvention may be varied somewhat fromthe 100 to 500 F. range if it is desired to obtain different amounts ofrubber solvent, VM' & P naphtha, or specialty naphthas. By narrowing theboiling range of the virgin naphtha to within 100 to 250 F., forexample, the process can be directed to obtaining rubber solvents almostexclusively. .On the other hand, by starting with a fraction boilingbetween 200 and 400 F., increased yields of VM & P solvents andspecialty naphthas may be produced. One embodiment of the inventioncomprises the treatment of the entire first fraction boiling up to'500"F. to produce a wide variety of products ranging from rubber solvents upto higher boiling specialty naphthas, including, for example, petroleumether 90140 F.', Special Textile Spirits l80-210 F., Light MineralSpirits 290-330 F., Stoddard Solvent 3l0-385 F., and High Flash DryCleaning Solvent 360400 F., all of which are non-corrosive, odorless,and meet the rigorous requirements of the industry, from high sulfurcrudes heretofore thought impossible of such treatment. Accordingly, theboiling range of the virgin naphtha may be:

varied considerably without departing from the spirit of the invention.

The virgin naphtha fraction selected from the crude is subjected to acatalytic hydrodesulfurization treatment carried out in accordance withwell known techniques at elevated temperatures. In the treatment, thesulfur content of the charge stock is removed in the form of a gasvirgin naphtha fraction subjected to hydrodesulfurization may containfrom about 1 to 7 per centby weight of sulfur. The charge may beintroduced to the catalyst catalyst per hour.

The products from the hydrodesulfurizatlon are subjected tostabilization wherein thehydrogen sulfide and any fixed gases areremoved and the resulting stabilized products are subjected to chemicaltreatment wherein contact is had with a slurry of an active metal oxideor metal salt capable of chemical combination with the remaining smallamount of corrosive sulfur compounds. Salts or metal oxides of metals ingroup I-B of the periodic table, particularly copper oxide or salts ofcopper, including copper suboxide (C1140), cuprous oxide of cuprite(CuzO),

. cupric oxide (CuO), and copper peroxide (CuOz-HzO) may be used in thischemical treatment. This second treatment may be carried out byemploying the reducible oxide or metal oxide in finely divided formdistributed 1 evenly throughout oriincorporatedwith a porous. supportvzone at from 0.5 to 10 liquid volumes per bulk volume of.

material, as, for example, the metal oxide may be. in finely dividedform dispersed uniformly through a porous silica or alumina support] Oneparticularly desirable method is to use the oxide in the form .of aslurry with a material capable of carrying the oxide in finely dividedform. Such materials include slurry oils ranging from.

a light oil to heavier, high viscosity oils. In certain instances otherorganic solvents may be used as the slurry medium as long as they do notaffect the process or enter into reaction with the sulfur. compounds insuch way as to deleteriously affect the finished naphtha. Thehydrodesulfurized products are mixed with the slurry of metal oxide andmaintained in contact at temperatures from 400 to 650Fffor periods oftime ranging from a few seconds to a minute. The preferred temperatureis about 450 F. The charging rates for this chemical contacting may varywithin wide limits and may be, for example, from 1 to 15 volumes-ofhydrodesulfurized product (C311 culated in the liquid form) per hourpervolume of contact mass.' The selection of the optimum rate or range ofcharging rates for any particular hydrodesulfurized product will dependlargely upon the concentration of sulfur compounds present and thepercentage of metal in the. contact mass. It is preferredto use lowerrates of contact within the above range Where larger quantities ofsulfur compounds are present or where smaller concentrations of themetal contact material are used.

T he chemical treatment may be carried out in any physical state, thatis, with the hydrocarbons in liquid or vapor form and the well knownsuspensoid, fluid, fixed bed, or slurry type of treatments may beemployed. At the end of the chemical treatment, portions of the refinedvirgin naphtha are removed and distilled to yield light hydrocarbons,rubber solvent, VM.& P solvent, mineral spirits, and heavy naphtha.

, Referring to Figure 2 for a specific embodiment of the invention, anaphtha charge boiling from about 110 to 450 F. obtained from a sourcrude is passed through line 2 into heat exchanger 4 and thence intocoil 6 of tube still 8. The preheated naphtha leaves tube still 8 vialine 10. Hydrogen enters the system at line 12, passesthrough line 14 tocoill6-of tube still 8 and thence into line 18. The preheated naphthaand hydrogen mix in line 20 and pass into either hydrodesulfurizationreactors 22 or 24. More than one hydrodesulfurization reactor is used sothat one reactor may be on stream while the other is regenerated. Thehydrogen is heated to the maximum temperature in the hotter coil 16 oftube still 8 and the naphtha fraction is heated to a lower temperaturein coil 6.

The mixture of naphtha and hydrogen enters reactor 22 or 24 at about 750F. and 250 pounds per square inch gauge. The hydrodesulfuriz'ed napthaand excess hydrogen leave the reactor under substantially the sameconditions through line 26, through heat exchanger 28 and heatexchanger. 4, through line 30 into stripper 32. In stripper 32 theproducts are at about 400 F. and

' 240 p. s. i. g.-and with theaid of added heat from reboilcr 34 thehydrogen and hydrogen sulfide are removed. The hydrogen and hydrogensulfide pass through line 36 and heat exchangervSS'into thefirst stageof Girbitol unit 40 for countercurrent contact with an agent designed todissolvev the hydrogen sulfide as an amine solution. Purified hydrogenpasses through'iline 42,.heat exchanger 38, and

' line 44 for recycle in the system. Hydrogen sulfide. is removedfromthe amine solution by the second Girbitol unit 46 and recovered atline 48. Amine solution is recirculated between units 40 and 46 vialines 50 and 52 through heat exchanger 54.

The gas-free; naphtha passes through line 56, heat ex changer 28, andline 58,'to the slurry treater 60. Pump 62 serves to circulate theslurry of metal salt or metal oxide and naphtha through the treater 60.Spent slurry is redrawn at line 64 and fresh slurry introduced at line66. The slurry: treating process is operated at about 450 F- ansiasubtaatial iPQ ti W e i all h heat, is supplied by the vaporized naphthaentering the system. The treatment occurs mostly in the circulatingsystem rather than in the treater 60, which acts more as a separator.Since very little treating or reaction occurs, the slurry does not needto be continuously regenerated.

The hydrogen added to the process may contain low boiling hydrocarbonsup to about 30 per cent by volume and any build-up of such components inthe process may be eliminated by absorption of same in oil or bydiscarding a portion of the recycle hydrogen.

The slurry-treated naphtha passes Via line 68 into distillation unit 70.Distillation unit 70 is operated to produce an overhead stream throughline 72, two side streams at lines 74 and 76, and a heavy naphtha bottomstream at line 78. The side streams 74 and 76 are processed in strippers80 and 82 to produce a VM & P naphtha at line 84 and a mineral spiritsat line 86. Any vapors from these side stream products are returned vialines 88 and 90. The overhead stream passing through line 72 issimilarly processed in stripper 92 to provide a rubber solvent at line94. A reflux stream passes through line 96 and is proportioned back todistillation unit 70. Light petroleum gases pass off at line 98.Suitable heat exchangers like 100 serve to cool the products.

As an example of the invention, the following experiments wereconducted: A virgin mineral spirits fraction was obtained from a Worlandcrude oil having 1.7 Weight per cent sulfur and an API gravity of 37.9.The fraction boiling between about 110 to 450 F. contained about 0.54weight per cent of sulfur at an API gravity of 55.7 and contained about15 volume per cent of aromatics, 35 volume per cent of naphthenes, and50 volume per cent of parafiins. This fraction was hydrodesulfurizedusing a cobalt molybdate catalyst under reaction conditions of about 750F. and 250 pounds per square inch under conditions of 3000 s. c. f. ofhydrogen per barrel of charge. The hydrodesulfurized product so obtainedafter hydrogen sulfide removal contained 0.05 per cent total sulfurcalculated as residual sulfur, including sulfide sulfur, and elementalsulfur, and, upon testing in the presence of copper under thedistillationcorrosion test, was found to give a darkened strip and waspositive and unsatisfactory. Test portions of this fraction were furthertreated with mercury to remove any elemental sulfur present but the testproduct still produced a borderline, unsatisfactorycorrosion-distillation test. A test treatment of the product with sodiumpolysulfide did not improve the distillation-corrosion test. The mainportion of this material was passed over a bed of cupric oxideprecipitated on bauxite (2.5 per cent CuO) at 450 F. and the productgave a negative distillation-corrosion test, but the product so obtainedhad substantially the same total sulfur content as the hydrodesulfurizedproduct. The odor was improved.

The hydrocarbon mixtures to be treated in accordance with this inventioncomprise any mixture of hydrocarbons regardless of source or chemicalconstitution which have a high content of sulfur or sulfur compounds.Such hydrocarbon mixtures generally have correspondingly high aromatichydrocarbon contents and as such are extremely difficult to treat forthe purpose of producing good fuels, naphthas, and kerosenes. The sulfurmay be present as elemental sulfur but is generally present as sulfurcompounds including hydrogen sulfide, organic sulfides, and disulfidesof aromatic naphthenic and polycyclic origin. By high sulfur content ismeant those hydrocarbon mixtures including crude oils having from 1.0 to3.0 weight per cent of sulfur present. Also included are those mixturesor fractions having as high as 5.0 per cent of sulfur. Such crude oilsor mixtures may have an API gravity ranging from about 20 to 40 orhigher.

Those skilled in the art will immediately appreciate that thecombination of treatments herein disclosed is capable of variation inits details without departure from the subject matter of the novelcombination herein described. The invention is not to be strictlylimited to the disclosure as set forth herein for illustrative purposes,but only as required by the appended claims.

What is claimed is:

l. The process for producing special solvent naphthas which pass thedistillation-corrosion test from hydrocarbon mixtures containingdeleterious sulfur compounds which comprises separating a virginfraction having a boiling range of about to 450 F. from said hydrocarbonmixture, subjecting said virgin fraction to hydrosulfurization at about500 to 800 F. in the presence of hydrogen and a catalyst comprisingcobalt molybdate under conditions such that hydrogen sulfide isproduced, separating the hydrogen sulfide so formed to produce ahydrodesulfurized product, subjecting said product to a chemicaltreatment in the presence of cupric oxide at about 400 to 650 F.,separating a purified product and fractionating said purified product toproduce fractions which pass the distillation-corrosion test.

2. The method in accordance with claim 1 in which said hydrocarbonmixture is a Worland crude oil having about 1.7 weight per cent sulfurand an API gravity of about 37.9.

3. The method in accordance with claim 1 in which said chemicaltreatment is carried out with said cupric oxide in slurry form.

4. The method in accordance with claim 1 in which said chemicaltreatment is conducted by contacting said hydrodesulfurized productswith said cupric oxide distributed on silica.

References Cited in the file of this patent UNITED STATES PATENTS1,837,963 Houdry Dec. 22, 1931 2,063,113 Morrell Dec. 8, 1936 2,151,721Schulze Mar. 28, 1939 2,202,401 Rosen May 28, 1940 2,574,449 Lorne Nov.6, 1951

1. THE PROCESS FOR PRODUCING SPECIAL SOLVENT NAPHTHAS WHICH PASS THEDISTILLATION-CORROSION TEST FROM HYDROCARBON MIXTURES CONTAININGDELETERIOUS SULFUR COMPOUNDS WHICH COMPRISES SEPARATING A VIRGINFRACTION HAVING A BOILING RANGE OF ABOUT 110* TO 450* F. FROM SAIDHYDROCARBON MIXTURE, SUBJECTING SAID VIRGIN FRACTION TOHYDROSULFURIZATION AT ABOUT 500* TO 800* F. IN THE PRESENCE OF HYDROGENAND A CATALYST COMPRISING COBALT MOLYBDATE UNDER CONDITIONS SUCH THATHYDROGEN SULFIDE IS PRODUCED SEPARATING THE HYDROGEN SULFIDE SO FORMEDTO PRODUCE A